


We're All Captains Here

by entanglednow



Category: Sherlock (TV)
Genre: Alternate Universe, Gen, Merlock, Mermaids, Mythical Beings & Creatures, Non-human
Language: English
Status: Completed
Published: 2014-02-01
Updated: 2014-02-01
Packaged: 2018-01-10 19:09:22
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,475
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/1163398
Author URL: https://archiveofourown.org/users/entanglednow/pseuds/entanglednow
Summary: <blockquote class="userstuff">
              <p>"If I remember correctly you spent the first thirty minutes of our acquaintance insisting that I wasn't real, and that you had, in fact, had some sort of mental break."</p>
            </blockquote>





	We're All Captains Here

**Author's Note:**

> Me and GoldenUsagi, because we both love crazy AUs, decided to try and write a story every month where Sherlock is something weird and unusual, then post it on the last day. January came up 'mermaid.' This is mine, but you should check out [Drowning is Boring](http://archiveofourown.org/works/1163426) too.

The therapist had suggested that it might be a good idea if John got away somewhere for a while, out of London, away from the noise and the people. She'd said it would be an opportunity to allow himself to heal, and decide what he wanted to do next, away from the pressure and expectation. London had been too expensive to stay in for long, and John hadn't wanted to call in any favours, he hadn't felt ready to deal with the conversations that would inevitably result. Though he'd wanted to refuse to follow her advice, on principle - the idea of it, the sea air, the isolation, the quiet, the idea had seemed sensible enough. Better than what he could see for himself here.

For all the optimistic suggestions that it would be an opportunity to meet new people, and make new friends, John honestly hadn't expected to, hadn't really wanted to if he was being honest. But even if he had - even if he had - he wouldn't have expected them to find him during a crisis, in the middle of the ocean, or that they'd size him up with brutal clarity within moments of meeting him. Though, at the very least, he would have expected any prospective new friends to have legs. That one had been a bit surprising.

Thinking back on it, 'a bit surprising' was something of an understatement.

"You people, your conversations go on for ages." There's a thump of irritation from the end of the boat, John can feel it vibrate beneath his feet, and Sherlock surfaces with barely a ripple. "The bottom of your boat is very dull, I thought you should know."

"What did you expect me to do, tell them to bugger off?" John checks to make sure the boat holding the always enthusiastically friendly Waldon brothers has drifted far enough that they can't see him any more, then makes his way to the back of his own boat. Where there's a bored mermaid - merman - balanced against the water-splashed line of the ladder, dripping all over the morning paper. He's trying to work out how to turn the pages without the paper going soggy and coming apart. He's mostly failing at it, and looks very annoyed about it.

"Hmm." Sherlock sounds as if he's not entirely sure what that means, but suspects the answer is still yes.

Even two weeks later, John's brain still wants to reject the idea that someone can be half man and half fish. He's a doctor, he knows better than most that it's plainly physically impossible, it's biologically impossible, it's probably anthropologically impossible. That doesn't change the fact that there's one currently reading page seven of the Southampton Daily Echo, six feet from him, tail swaying and twisting in the water, sending currents slapping against the back of the boat. Impossible things aren't usually allowed to steal your stuff. It's unfair.

"It depends, would saying that have encouraged them to leave sooner? You're far too obsessed with social niceties. They're clearly important to you, though I haven't come to a conclusion as to why yet." Sherlock attempts to dry his fingers on the sports section, dark nails leaving fine rips in the paper, the pages disintegrate in clumps. "Are people normally that persistent around you?" Sherlock makes it sound like John was being friendly on purpose.

"They're only just out of sight, you're lucky they didn't _see_ you." John makes his way closer, pushing things out of the way, in case Sherlock's curiousity knocks something into the water again.

"I didn't come up until you relaxed. Your long distance vision's probably better than mine out of the water." He pauses like he's thinking about it. "I haven't had the opportunity to dissect a human eye yet. The birds tend to steal them from the surface, the fish and the crabs get them underneath." He makes a stabbing, or a clawing, gesture with his hand, something rather more practiced and natural than John likes the look of, if he's being honest. He wonders if he should have an opinion about Sherlock's hobby of 'collecting' bodies for research, decides probably not. At least not at the moment, there's a possibility it'll come back to haunt him later though.

"You realise that, at some point, someone's going to notice that I don't, in fact, have any interest in fishing, and that I very rarely come back with any fish." And that occasionally he still trips over parts of the boat.

"In my observation that's rather standard for hobby fisherman." Sherlock twists until he can brace himself against the back of the boat, folds a hand round the strut that holds the ladder there. He's making no effort at all to disguise the fact that the half of his body below the water line isn't human in the slightest. John supposes he doesn't think he needs to bother, since John already knows he's half fish. Still, he learned fairly quickly that the lack of obvious self-preservation instincts, and the tendency to be insanely reckless is a purposeful dare to the rest of the world to catch him, rather than stupidity or naivety. John thinks he liked it more when he thought it was stupidity.

"How have you not ended up in anyone's net by now, seriously?" It's an honest question. John doesn't see how any mythical creatures can be this reckless and not have ended up in some sort of zoo, or worse, stuffed and on someone's wall by now. Which is an exceptionally horrifying thought.

"Very sharp nails, very sharp teeth," Sherlock tells him, clicking the second as a demonstration. "You fret a lot, John. Besides, if you didn't have a boat I wouldn't be able to converse with you. You'd miss me terribly."

John would certainly miss feeling sane on a daily basis.

"I wouldn't have a boat if Captain Kitman hadn't left me his, and I still have no idea why he did that. Who leaves someone a boat? Who leaves someone who doesn't know how to drive - how to _sail_ a boat a boat?" He'd barely been in town a few weeks, and his entire relationship with the man had been a few awkward conversations, while ferrying John out to look at people who'd had some sort of horrible accident with a hook, or been knocked out by someone getting over-enthusiastic with boating equipment. And once, memorably, to remove a fish from a compromising place.

"Yes, what a happily fortuitous accident, Captain-Captain Watson," Sherlock clips out. "I think you're doing remarkably well with your new skill set."

John eyeballs him as he tries to fold the paper - folding doesn't seem to come naturally to his hands. Probably not a skill set you develop underwater.

"Did you have something to do with it?"

"Hmm," Sherlock agrees. "I would have broached it with you, but I've noticed you sometimes have trouble accepting new ideas."

That is incredibly unfair, considering how well John has accepted an awful lot of things lately. His accepting insane things quota has been spilling over for at least a month. He thinks the fact that he hasn't had any type of breakdown yet deserves some sort of recognition.

"What? I can accept new ideas! I accepted you didn't I?"

"If I remember correctly you spent the first thirty minutes of our acquaintance insisting that I wasn't real, and that you had, in fact, had some sort of mental break."

John will admit, that's a fair description of how their first meeting went. But that was their very first meeting, before anyone had braced John for _mermaids_ before he'd even had any idea that he'd need to be braced for mermaids. He thinks he can be forgiven for taking a moment to try and make 'mermaids are real,' fit with the rest of his, up to now, completely sensible and normal and ordinary ideas about the world.

"Then you threw a fish at me," John remembers, because he thinks he might be, in some small way, still annoyed about that. "A very large fish, with sharp parts." He's not up on his fish-identification yet, so that's the best he can manage.

Sherlock looks amused somehow, without any of the ordinary human signs of amusement.

"It seemed the most expedient way to get your attention at the time."

"And you blame me for that do you?"

"For being dull, not at all. I expect it's your legs, legs clearly make you stupid." It's not the first time Sherlock's made that assertion, but it's the first time he's sounded certain about it.

"Legs do not make you stupid." John, being the only member of a leg-having species in the vicinity, feels like he should go to bat for them.

Sherlock's untranslatable, clicking response to that is clearly calling him a liar.

"It was a huge fish," John says instead. "You could have given me _concussion_."

The merman equivalent of an eye roll appears to be a slow curl and uncurl of tail. This is the first time John's gotten a good look at the gesture. It looks...oddly ruder when not performed underwater, more obvious, and he feels like he should be offended. Another mermaid would probably be offended.

"No, don't do that, that's completely unfair. Say you came across..." John flounders for a minute, for something that would seem wildly out of place on the ocean. "I don't know, say some sort of giant man, a hundred foot tall, just swimming in the ocean." He gestures out into the expanse of water. "Out there, just swimming."

Sherlock's tail flicks sideways, John thinks that's supposed to be mockery.

"Don't be absurd, John."

"No, see." He wags a finger at him. "You and I both _know_ that that's absurd, but just say - just hypothesize that you come across it one day, while swimming, hmm? This absurd and impossible, you think, thing. What do you do?"

Sherlock's expression seems to be saying 'I'm going to humour you, because of your legs.'

"I suppose I'd have to accept the evidence then wouldn't I."

"Like I did with you?" John says triumphantly.

There's really no need at all for the brief movement that sends a drift of sea water and slime in his direction. John ignores it, because he knows Sherlock wants him to comment on it, and he's not going to give him the satisfaction.

"Yes, see that was exactly how it was for me, with you, and your -" a hand gesture really doesn't do Sherlock justice. But John has to try at least. "Various things. But now, here I am, sitting here in a boat which I now own, my own boat, having a conversation with a mermaid."

Sherlock makes some sort of brief, high-pitched noise that hurts John's ears, annoyance, irritation, something making rude assumptions about his parentage. He has no idea, since he doesn't speak whatever language travels underwater. He's not sure he could even reproduce half the noises Sherlock can. It's sort of amazing Sherlock manages one of theirs so well.

"Merman if you must. I know it's difficult for you to tell, without the genitalia you're all obsessed with, but try to keep up."

"How long did it take you to learn English anyway?" John asks curiously. "I mean sound travels through water completely differently to air. I'm surprised you managed it, to be honest."

Sherlock looks insulted, and that's a facial expression which seems to translate perfectly well.

"Ugh, English, it took me a while to work out that you had different languages at all. It was all just noise to me at first. I thought you just had millions of words for things, like a constant stream of rubbish. It was vexing to have to sort them into different groups, regions -" Sherlock waggles his fingers, the sharpened edges of his nails glinting in the sunlight. "Accents."

Sherlock hauls himself up onto the boat, water streaming off him. The long end of his tail coils around the bottom of the ladder in a lazy curl, elbows balanced on the bottom of the boat, while he rifles through John's bag. John has never had the opportunity to see him completely out of the water before. He's much longer than he'd imagined, scales a sort of iridescent grey/green with blue highlights, fins in strange places. The rest of him could pass for human, mostly, if you skip over his nails and the strange colourless not-quite-right shine of his eyes.

"You're staring, rather obviously." Sherlock sounds amused rather than annoyed. He barely looks up from his rifling.

"Sorry, it's just, well I mean - I'm a doctor, I can't really help thinking about how you...fit together. Which bones are the same, how you manage to be a mammal and fish at the same time." He's not entirely sure if that's a tactful way to phrase it. He doesn't want to make Sherlock sound like a science experiment, no matter how fascinating and impossible he is. But all Sherlock does is look at him from under his soaking wet hair, in a way that's considering.

"I suspect I could arrange for you to examine the remains of one of us. But we dissolve fairly quickly, so you'd have to make your observations in some haste."

John's honestly not sure whether to be horrified, flattered, or fascinated by that offer. He settles for all three, which isn't an entirely comfortable mix.

"Now you look disturbed. We don't hold any affection for dead bodies, John. In fact, we used to eat them not long ago."

"Cannibalistic mermaids," John mutters to himself, slowly, just one more thing on the list he can never tell anyone about, ever. Not that anyone would ever believe him. He's going to turn into one of those cautionary tales about lonely men who go crazy at sea - and start rambling about mermaids and sea monsters. Oh god, there are probably sea monsters too.

"Not any more," Sherlock says testily, and for a second John thinks he's said that last part out loud. "As I just told you." He's finally found what he's looking for, the maps John's had packed away in there for a while. Sherlock shakes them out, and then makes a frustrated noise when he immediately drips on them. "Lamination, John, you might want to look into it." He mutters something else about the human obsession with paper that John doesn't entirely follow.

"What are you looking for?" John asks, awkwardly crouching down next to him.

Sherlock doesn't answer, simply hands him the paper he'd been reading, crudely folded over, missing pages and half covered in damp patches and small tears from his nails.

" _'Local man missing at sea'_ " John reads. "Yes, I remember hearing about that. I don't think they've found him yet. "

"I don't expect so," Sherlock offers. "Though I'm fairly certain I know where his boat has drifted to, and it's nowhere near any of the search areas hastily plotted out by the local constabulary. I know because I've been watching, there hasn't been much else to do. I'm surprised no one else has made the connection with the first disappearance."

John frowns, and Sherlock makes a gesture that he interprets as 'keep reading.'

"James Howe, 38, a fisherman by trade, was last seen Thursday morning - "

"Not that," Sherlock jabs him with a finger in frustration. "Later."

John sighs and skips ahead, trying to find whatever Sherlock had clearly interpreted as important.

" - though police have not released any statements so far, the fact that his father, Richard Howe, disappeared in the same way in 1988 - Sherlock I thought you didn't involve yourself in human mysteries. Why are we solving a mystery? This is a disappearance, the police are going to be involved. Aren't you supposed to worry about being seen?"

Sherlock gives an irritated headshake, as if John's worrying about unimportant things again.

"I would have thought you'd want to find a missing man."

"I do, I mean of course I do, but there'll be boats and the police - " John frowns again and lowers the paper. "Do you really know where he is?"

Sherlock makes a gesture that probably means a lot more underwater, some sort of jerky hitch of his elbows.

"I'm confident that I know where he went, and my knowledge of the currents and water line activity exceeds the local police, so yes." Sherlock slides backwards until he can slip into the water again, leaving the maps stretched out where his body had been, slowly soaking through.

John peels them off the deck with a sigh.

"I'm not going to win this one am I?"

"That's the spirit, John."

-

They find James Howe's boat exactly where Sherlock said it would be, floating powerless and uncontrolled. John cuts the engines, at what he thinks is a safe distance, boats tend to drift rather more erratically than he'd first expected. But they're close enough to tell that there's no activity on board. It looks abandoned, from what he can see of it. Of course that doesn't conclusively mean there's no one on board.

"How did you know?" he asks curiously, and he's not sure why he's talking quietly. If the boat really is empty then they're miles from anyone that might hear them. But Sherlock doesn't seem to want to share that fact yet. He just shakes his head, and then eases round John's boat, as if debating whether to head across on his own.

"If there was blood in the water I'd be able to smell it, everything above the water line I lose most of my olfactory senses. Vexing. You're going to have to swim over there."

John's pointed look apparently doesn't translate very well.

"You want me to leave the boat? Granted I'm fairly new to boats, but I know you're not supposed to just swim off and leave them drifting on their own. That's breaking some sort of sensible boat owner rule, I know, there was a course."

Sherlock splashes water in his general direction, impatiently and possibly not deliberately.

"I can swim faster than your boat, if it chooses to make some sort of dramatic escape I shall return you to it, do stop fussing, John."

Howe's boat, The Crimson Room, is still drifting, now silent and oddly menacing to their left side (or port, or starboard, he keeps bloody forgetting which is which, and it's probably important if this is going to be a thing.) John swears and heads to the back of the boat, pulling off his jumper and boots, before staring down into the dark water, where Sherlock is doing his impersonation of a duck, perfect stillness above, restless motion below. John is almost certain he wouldn't appreciate that comparison, but it's unbearably fascinating to watch. Not to mention a little frightening, if he's being honest. He's never been in the water with Sherlock before, he feels strangely breathless and unmoored at the thought, like a boat on the ocean.

Sherlock blinks very slowly, John thinks he's disappointed him.

"Are you afraid to get in the water with me? Really? My physiology isn't catching."

"No - no, that's not what I'm worried about, I just - I've seen what you can do when you're not paying attention." For all the old myths about drownings and sirens, mermaids in folklore always have delicate, floaty tails that curl up underneath them. They sit on rocks, and comb their hair, and look about as inoffensive and harmless as ridiculous mythical creatures tend to. Sherlock is not delicate and floaty. Sherlock's tail looks like it could smash every bone in John's body, and he's personally seen his nails punch through an oyster shell. He feels oddly fragile all of a sudden. What happens, he wonders, if you drop a monkey into a shark tank?

"Yes, I'm aware of how fragile your leg bones, and assorted boneless parts are. I know how to avoid things when I swim, astonishingly enough. You'll be perfectly safe." Sherlock lifts a hand up, pale and streaming water, dark nails pointing upwards.

It's an oddly human gesture of impatience, and John finds himself grumbling as he strips to his jeans and reaches to take Sherlock's hand. It's cold, slippery-smooth, not quite human enough to pass, but it grips reassuringly as he eases himself into the water. The water which is, in fact, bloody cold. John spends a second breathing through his teeth and treading water to acclimatise to it. Before he starts swimming.

"I love watching humans swim, you try so hard." Sherlock is clearly dawdling for his convenience, he's barely moving to keep the pace John sets. "Like baby seals."

"Oh, and you're just a model of grace on land I expect," John complains, accepting the fact that he looks a fool, since there's nothing else to be done about it, spitting water and stroking for the abandoned boat. "Flopping around, without a centre of balance."

Sherlock huffs a strange laugh, and John suspects he's just won a point.

Once they reach the back of the boat John's up the ladder easily enough, while Sherlock has to pull himself up the hard way, tail curling and then straightening to give him enough of a shove to reach the lip. He looks much clumsier trying to get a hand up to brace himself on the slippery deck, and John's oddly reassured by that. He finds James Howe, laying face-down in a pool of darkening blood in the cabin. John checks for a pulse, with no real hope of finding one.

"He's dead," he calls back. "He's been dead for a while."

"Obviously." Sherlock doesn't sound surprised in the slightest.

"But he's been missing for two days?" John wonders. "What the hell is he doing here, this is nowhere near where he was supposed to be?"

"I'd imagine he went to great pains not to found. If you investigate I suspect you'll find the radio disabled in some way and any documentation missing." There's a squeak of wet skin and scales on plastic, and the thump of something hitting the bottom of the boat. Sherlock is about as close as he's going to get without being completely out of the water.

John walks around the body, carefully, without disturbing anything. He's seen more than a few dead bodies, but this is probably his first murder victim.

"Looks like he was struck from behind. Sherlock, this is no longer a disappearance, this is a murder and I have to call someone."

"Of course, but it'll take them some time to get here."

"Yes, and you need to be gone when they do. You can't be seen, you know that." That's the last thing they want, that's the last thing John wants, crazy as it sounds. Though Sherlock doesn't seem half as worried as John because all he gets is a sigh and a tail-curl of impatience.

"First show me what was in his pockets."

"That's interfering with the body, Sherlock, I can't -"

"He's not going to protest," Sherlock says testily.

Not exactly what John was aiming for there.

"For the police, oh for god's sake, you have wet hands," John reminds him.

Sherlock makes another impatient gesture.

"We're on a boat, things will get wet, John."

"Also, fingerprints, what about fingerprints? This is effectively a crime scene."

"Don't have any, so irrelevant."

John gives in and starts carefully rifling through the dead man's pockets, wondering how socialising with mermaids had somehow made him less worried about bending the law.

"Wallet, keys, maps, mints, no phone, must be in the cabin somewhere, or our murderer took it, or threw it into the ocean?"

Sherlock's already taken half of John's discoveries, he's currently searching through James's wallet.

"This is fascinating, out of the water the evidence just...stays, you can look at it for positively ages."

John's going to complain about how he's probably destroying said evidence, but there's a thrum of something like excitement in Sherlock's voice. He remembers, strangely distantly, that he's talking to a mermaid, and suddenly he couldn't give a toss what the police think. What must it be like, trying to explore a world that's so different from everything you're used to. To do it anyway, regardless, because you wanted to know how it worked.

"Not always," he finds himself saying. "We have weather on land too, y'know, also animals that eat things."

"Howe, when would you say he was killed, as precise as you can make it?"

"I don't know, no more than two hours I'd say." John leaves him to his rifling while he calls the police, and the coastguard.

Sherlock disappears into the water, and remains gone for long enough that John thinks he's not coming back. He makes his way back to his own boat. Which he's starting to get more attached to than he ever suspected he would. Sherlock surfaces a minute later, holding the waterlogged, black lump that is James Howe's phone. Which he passes up - John's fairly sure it's a lost cause, but the fact that Sherlock managed to find it at all is pretty astonishing.

"That was pretty impressive."

"I knew nothing would eat it, and your electronics are heavy enough, and of a basic enough shape, that they tend to sink straight down. It took more time to ascertain where the boat had been two hours ago. Someone thought the phone contained incriminating information. That can be recovered via other means, yes, some sort of records?" There's a frustration in the way Sherlock says it, as if some human things are still nebulous and uncertain to him.

"I should think so, yes, look you should probably be gone before they show up."

"Frustrating." There's a swing of lower body that ends with a thump against the bottom of the boat.

"I know, but I think mysteries on land are a lot more complicated than the ones you get to solve in the ocean, dangerous even."

Sherlock says nothing, just drifts at the end of the boat with a frown on his face that looks very human.

"Dangerous doesn't bother me. But the water isn't exactly safe for you either, John Watson, you have no idea what's out there."

Sea monsters, John thinks, and he stares back at the shore, where he can just see boats in the distance. Civilisation, drifting in his direction.

"Could be dangerous," he mutters to himself. "I think I'd quite like to find out. Besides, you promised to help me name my boat after all. I have a registration number, but that's it. And I can't just call it SU-221B forever."

"Indeed not," Sherlock says, with one of his odd, sharp smiles.

The coastguard signals him with a low drone. John very carefully puts a hand on top of Sherlock's head, and pushes him underwater.


End file.
